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Sunday, December 14, 2008

Free Fallin' Yet Again

Apparently a physics teacher and 9-11 Troofer named David Chandler "discovered" that WTC-7 had been in freefall for part of its collapse. Never mind that the Troofers have always claimed it was in freefall (or, humorously, faster than freefall) for the entirety of its collapse, they greeted this news as evidence that backed up their fruitcake theories of controlled demolition.

To stimulate further discussion, may I also point out that we have accepted the possibility of very high accelerations, approaching 1 g, all along. See this thread for an example of such a discussion, concluding that the actual descent rate could indeed wind up within the margin of error of "free fall," yet have nothing whatsoever to do with explosives. I remind readers that the thread starter is under no circumstances a "government stooge" or what have you, but instead approached the problem from the opposite initial viewpoint.

Furthermore, supposing there were explosives used, one expects their placement would result in a very similar core damage sequence to the one that NIST found likely as a result of fire. This suggests that NIST and a typical CD hypothesis would be indistinguishable on the basis of a roofline velocity test. Instead we look to other tests, such as the sound and blast effect on windows, and these rule conclusively against explosives.

Tfk points out:

However, the crucial point here is that Chandler's results agree EXACTLY with NIST's. Chandler didn't have to do this work at all. He replicates EXACTLY NIST's graph shown in Fig 12-77 on page 603 of NCSTAR 1-9 (Vol 2). This is page 265 of the downloadable pdf file. The slope of the best fit linear curve is "32.196". (Keeerist, don't they teach kids about "significant digits" any more??!!! It should be 32.2, probably ±0.5 or so.) A glaring omission in both papers is an error analysis - a CRITICAL component of any competent engineering paper.

Conclusion: Freefall doesn't prove anything. Indeed, I have consistently argued that Troofers just assume that controlled demolitions fall at freefall speed when they do not.